The present invention relates to valve lifters for use with internal combustion engines, and, more particularly, to a valve lifter which accomplishes cylinder deactivation in internal combustion engines.
Automobile emissions are said to be the greatest source of pollution in numerous cities across the country. Automobiles emit hydrocarbons, nitrogen oxides, carbon monoxide and carbon dioxide as a result of the combustion process. The Clean Air Act of 1970 and the 1990 Clean Air Act set national goals of clean and healthy air for all and established responsibilities for industry to reduce emissions from vehicles and other pollution sources. Standards set by the 1990 law limit automobile emissions to 0.25 grams per mile (gpm) non-methane hydrocarbons and 0.4 gpm nitrogen oxides. The standards are predicted to be further reduced by half in the year 2004. It is expected that automobiles will continue to be powered by internal combustion engines for decades to come. As the world population continues to grow, and standards of living continue to rise, there will be an even greater demand for automobiles. This demand is predicted to be especially great in developing countries. The increasing number of automobiles is likely to cause a proportionate increase in pollution. One major challenge facing automobile manufacturers is to reduce undesirable and harmful emissions by improving fuel economy, thereby assuring the increased number of automobiles has a minimal impact on the environment. A method by which automobile manufacturers have attempted to improve fuel economy and reduce undesirable emissions is cylinder deactivation.
Generally, cylinder deactivation is the deactivation of the intake and/or exhaust valves of a cylinder or cylinders during at least a portion of the combustion process. Cylinder deactivation is a proven method by which fuel economy can be improved. In effect, cylinder deactivation reduces the number of engine cylinders within which the combustion process is taking place. With fewer cylinders performing combustion, fuel efficiency is increased and the amount of pollutants emitted from the engine is reduced. For example, in an eight-cylinder engine under certain operating conditions four of the eight cylinders can be deactivated. Thus, combustion would be taking place in only four, rather than in all eight, cylinders. Cylinder deactivation is effective, for example, during part-load conditions when full engine power is not required for smooth and efficient engine operation. Studies have shown that cylinder deactivation can improve fuel economy by as much as fifteen percent.
Conventional methods of achieving cylinder deactivation have been accomplished through modification of various portions of the valve train, and have typically required the addition of components thereto. These conventional methods have typically not fit within the space occupied by conventional drive train components. Thus, the conventional methods of implementing cylinder deactivation have required modification and redesign of engines to provide the additional space within which to house components used to achieve cylinder deactivation.
Therefore, what is needed in the art is a lifter-based device which accomplishes cylinder deactivation.
Furthermore, what is needed in the art is a device which accomplishes cylinder deactivation and is designed to fit within existing space occupied by conventional drive train components.
The present invention provides a split-body deactivation valve lifter for use with an internal combustion engine.
The invention comprises, in one form thereof, a lower body having a substantially cylindrical base and an elongate column extending in an axial direction a predetermined distance above the base. The base is associated with a cam of the internal combustion engine and converts rotary motion of the cam to vertical motion of the lower body. A substantially cylindrical upper body defines an axial column bore therein. A portion of the elongate column of the lower body is slidably disposed within the column bore. The upper body is associated with a valve of the internal combustion engine. The upper body is normally coupled to the elongate column of the lower body to thereby transfer vertical movement of the lower body to vertical movement of the upper body. The upper body is selectively decoupled from the lower body such that vertical movement of the lower body is not transferred to vertical movement of the upper body.
An advantage of the present invention is that it is received within standard-sized engine bores which accommodate conventional valve lifters.
Another advantage of the present invention is that the deactivation pin assembly includes two pin members, thereby increasing the rigidity, strength, and operating range of the deactivation valve lifter.